Abstract: Ammonium nitrite is commercially produced by contacting a gaseous stream containing nitric oxide, nitrogen dioxide and oxygen with an aqueous solution containing a basically reacting ammonium compound in an absorption system. However, at normal production rates, serious problems have been encountered because of the emission of unreacted nitric oxide which causes pollution of the atmosphere. It has now been found that by adding controlled supplemental quantities of nitrogen dioxide to the absorption system, nitrogen oxide emission is substantially reduced.